1. Field of the Invention
The present invention relates to a cleaning unit and a method for cleaning a substrate such as a liquid crystal display (LCD) glass substrate or a semiconductor wafer.
2. Description of the Related Art
Generally, when a liquid crystal display is fabricated a sequence of processes using photolithography technology is used for forming an ITO (Indium Tin Oxide) thin film and an electrode pattern on a LCD substrate (glass substrate) in the same manner as the fabrication of semiconductor devices. In the photolithography process, a circuit pattern is reduced. The reduced circuit pattern is transferred to photoresist. The resultant photoresist is developed.
In such a sequence of processes, resist solution is coated on a glass substrate. Thereafter, an exposing process and a developing process are performed. Before such processes are performed, it is necessary to clean the front surface of the glass substrate on which the resist solution is coated so as to prevent a defective circuit pattern, wiring short-circuit, out-of-focus state in the exposing process, and particles from taking place.
Thus, in a resist coating and developing system, a cleaning unit is disposed. In a conventional cleaning unit, an arm is disposed on one side of a glass substrate held by a holding means such as a spin chuck. While the glass substrate is rotated, a brush or a nozzle disposed at the edge of the arm is moved to an upper position of the upper surface of the glass substrate so as to clean the front surface of the substrate. The cleaning operation using the brush is referred to as scrubber cleaning operation. The cleaning operation using the nozzle is referred to as mega-sonic cleaning operation.
However, in the conventional cleaning unit, since the arm is held on one side thereof, the strength of the cleaning unit is weak. In particular, as the size of LCD panels becomes large, the cleaning area becomes large. Thus, the length of the arm should be increased. However, when the length of the arm becomes large, the arm further weakens. Moreover, in most conventional cleaning units, only one brush or nozzle is disposed at the edge of the arm. Thus, the cleaning areas of the conventional cleaning units are not wide. In other words, it takes a long time to clean the entire front surface of a glass substrate.